The invention relates to a printing plate holding device for an offset duplicator.
With the prior art devices, when employing a straight printing plate formed with no perforations, control of distortion or lateral displacement of the plate cannot be carried out so that displacement tends to occur at the tail edge of the plate during printing operations, even if the plate has been accurately formed. Accordingly, it has been proposed in U.S. patent application Ser. No. 251,450, now U.S. Pat. No. 4,391,193, to control the lateral displacement and/or the distortion or twisting of the printing plate by controlling the axial and/or circumferential displacement of the clamp base, between which base and the clamp plate the edge of the printing plate is clamped. With this construction, however, as the clamp plate should be strongly urged against the clamp base in order to prevent the printing plate from being disengaged during the printing operations, the clamp plate is rapidly closed with a strong force when clamping the printing plate so that the printing plate tends to be clamped in a twisted state, and further, a strong force is required to open the clamp plate.